Thiollier's Concoction

[Terrifying Turnip]

Does this item have a use in any of the NPC questlines? I haven't found one yet.

[paincanbefun]

right? i'm so curious to use it but...

[Detective Costeau]

Keeping it spoiler free:
Yes.

[Goro]

if you don't care about spoilers:

using it on a NPC in jagged peak will progress their questline and, should you do the correct steps, will give you a unique incantation and 1 spirit ash. But doing this also locks you out of getting the other rewards of the NPC

[Ironslayer541]

Yeah it lets you fast travel to a site of grace when your in a dungeon.

[juicy]

its the cool way to respawn at a grace now